1. 10-4 Triangles pages 428-431 Indicators  G3b- Use triangle sum relationships to solve problems. G4- Determine necessary conditions for congruence of triangles.

2. A triangle is a figure with three sides and three angles. The sum of the measures of the angles of a triangle is always 180º. 1 + 2 + 3 = 180º 2 31

3. Example An airplane has wings that are shaped like triangles. Find the missing measure. 1 + 2 + 3 = 180º 112º + 47º + x = 180º 159º + x = 180º - 159 - 159 x = 21º 112º 47ºxºxº The measure of the wing’s third angle 21º.

4. Classify Triangles Using Angles Acute All acute (<90º) angles Right 1 right (90º) angle Obtuse 1 obtuse (>90º) angle

5. = = =

6. Classify each given triangle by angles and sides acute, equilateral acute, scalene Right, scalene acute, isosceles Obtuse, scalene